Conventional padlocks, as shown in FIGS. 1, 2, 3, generally comprise a key hole block 10, a locking mechanism 1, a bolt 12 and a shackle 13 as the main components. At the top of the key hole block 10 a curved push block 100 is provided, and on the push block is positioned the bolt 12, which elastically contacts the pushing block 100 by means of a spring 120. The bolt 12 has a front end 121 located in a groove 130 formed in the toe of a shackle 13 in the locked position, as shown in FIG. 1.
When the contact surface of pin tumbler pushers 110 in the locking mechanism 11 and pin tumblers 111 become oriented in a straight line with the cylindrical touching surface 14 between the locking mechanism 11 and the key hole block 10, the key hole block 10 can be rotated by a correct key, causing the pushing block 100 to rotate through a certain angle to retract the bolt 12, thereby separating the front end 121 of the bolt 12 from the groove 130 in the shackle 13, in the unlocked position as shown in FIG. 2. The spring 120 moves the bolt 12, and, accordingly, rotates the key hole block 10, causing the front end 121 of the bolt 12, the pin tumbler pushers 110 and the pin tumblers 111 to return to their original positions. In these positions, if the shackle 13 is pressed down, the groove 130 can be engaged by the bolt 12 to lock the shackle 13.
However, the conventional padlocks are considered to have the following shortcomings:
1. A shim can be inserted in the key hole block 10 to illegally unlock it; and,
2. An electric drill can bore a hole through the curved contact surface of the key hole block 10 and the locking mechanism 11 to break the pin tumbler pushers 110 and the pin tumblers 111 to unlock it.